With avoidance of sunlight exposure due to lifestyle changes and concerns regarding skin cancer and the resultant widespread use of sunscreen, very few Americans are meeting their needs for vitamin D either through skin photosynthesis or dietary intake. A study published by the Centers for Disease Control (CDC) and our laboratory at the Medical University of South Carolina (MUSC) revealed that 42% of African American women in their childbearing years exhibited a deficiency of D vitamin (hypovitaminosis D) (1). Using new guidelines of optimal vitamin D levels, more than 90% of African American women now suffer from vitamin D deficiency (2). Science News (October 2004) called vitamin D deficiency a "silent epidemic" in America, with no group unaffected (3). Deficiency during pregnancy has profound effects on the developing fetus. Vitamin D deficiency affects other systems besides bones: it is associated with later, lifelong sequelae, with notable increased risk of autoimmune diseases such as rheumatoid arthritis (4), multiple sclerosis (5,6), type I diabetes (7,8), and certain cancers (7,9-14). Prevention and intervention studies only recently have been undertaken (3). A reexamination of dietary vitamin D requirements of various vulnerable populations in the U.S. is desperately needed (2,3). As a representative community with a diverse population, Eau Claire Cooperative Health Centers in South Carolina (ECCHC) serves a large percentage of African American as well as Caucasian and Hispanic women and children considered to be at high risk for vitamin D deficiency. ECCHC has eight clinics providing 1o care services to patients with special emphasis on Pediatric and OB/GYN services. Defining the prevalence of vitamin D deficiency in this patient population and the optimal vitamin D supplementation strategies for these women and their infants will become the prototype for recommendations applicable to other communities throughout the U.S.